The appeal of the aloe peel

Aloe vera is one of the most popularly grown plants. Its succulent leaf tissue finds use in food, health and cosmetic industries with a global market size of more than $2.5 billion annually. But while aloe vera gel – the polysaccharide-rich inner leaf tissue – is high in demand, the peels are often thrown away as waste.

A team of researchers led by Debasish Bandyopadhyay, Professor at the University of Texas Rio Grande Valley in the U.S., accidentally discovered that the peels, or rinds, can fend off bugs. Subsequently, in the lab the team identified several bioactive compounds in the extracts from the peels. The work, presented at the fall meeting of the American Chemical Society in San Francisco on August 15, may help find a useful application for millions of tonnes of aloe vera peels discarded as agricultural waste every year.

"When we visited a nearby aloe vera production facility, we noticed that insects had avoided the aloe leaves while destroying the foliage of other plants. Based on this observation, we hypothesised that the aloe rinds...must be possessing certain defence chemicals," Bandyopadhyay told Shaastra.

Currently, aloe peels are used to create biomass to help improve the quality of soil at aloe farms. Bandyopadhyay's team explored the possibility of recycling the peels to develop a natural pesticide to protect crops in the tropical and sub-tropical parts of the world threatened by insect pests. It could work as an environment-friendly alternative to the disposal of peels while creating additional revenue streams for aloe vera producers.

During experiments, the team identified over 20 compounds in the aloe vera rinds. Many of these had antibacterial and antifungal properties. However, among these were some compounds with known insecticidal properties, such as octacosanol, dinoterb, arjungenin, nonadecanone and quillaic acid.

These compounds, the scientists concur, could be contributing to the beneficial effects of the aloe rind. While the identified compounds are not toxic, chemical investigation of methanol and aqueous extracts is still ongoing; both show strong insecticidal activity.

The researchers plan to test these insecticidal compounds in fields against agricultural pests. They are also exploring whether these compounds have anti-mosquito and anti-tick properties, which could potentially lead to the development of an insect repellent for consumer use.

"Currently, the evaluation of mosquitocidal and anti-tick activities is in progress. We plan to carry out insecticidal evaluation on other pests such as locusts, Japanese beetles, corn rootworms, Mormon crickets, Colorado potato beetles, etc., to generalise the use of aloe peel-based insecticides," Bandyopadhyay says.